From 7bbec6c4b51d2323459203510028e8344f79e126 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 19 Mar 2020 16:51:46 -0500 Subject: [PATCH] leds: leds-pwm: Replace zero-length array with flexible-array member The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Signed-off-by: Pavel Machek --- drivers/leds/leds-pwm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/leds/leds-pwm.c b/drivers/leds/leds-pwm.c index 6caf8bea8cd5..6c8a724aac51 100644 --- a/drivers/leds/leds-pwm.c +++ b/drivers/leds/leds-pwm.c @@ -39,7 +39,7 @@ struct led_pwm_data { struct led_pwm_priv { int num_leds; - struct led_pwm_data leds[0]; + struct led_pwm_data leds[]; }; static int led_pwm_set(struct led_classdev *led_cdev,